Efficacy of insulin-like growth factor I levels in predicting the response to provocative growth hormone testing.
Clinical testing of growth hormone (GH) sufficiency is a controversial area in endocrinology. Due to the episodic nature of endogenous GH secretion, diagnosis of GH deficiency has been defined as a failure to achieve normal GH levels in response to at least two stimuli. This testing is associated with significant patient morbidity and cost. We analyzed our experience over a 4-y period to determine whether clinical or biochemical variables could be used to predict the results of a specific GH testing procedure. Of 180 cases analyzed (67% male, mean age 8.89 +/- 4.39 y, range neonate-16 y), eight cases had incomplete GH testing results. Of the remaining 172, 19 were GH deficient (GH level less than 7 ng/mL). Younger age, higher body mass index and a greater degree of bone age delay were characteristic of the GH-deficient population; however, none of these variables alone was of diagnostic utility. Serum IGF-I level was below the normal range for 81% of the GH deficient and 47% of the GH-sufficient children; and was the only single variable that provided a reasonable between-group distinction. Discriminant analysis resulted in development of a new variable, based on IGF-I z scores, chronologic age, degree of bone age delay, and body mass index, which would have allowed exclusion of GH deficiency without provocative testing for 58% of the GH sufficient population, whereas permitting the diagnosis of GH deficiency for all GH-deficient subjects. Our data are dependent on the IGF-I assay method and the clinical definition for GH deficiency; therefore, the calculated predictive values are not applicable to all clinical populations.(ABSTRACT TRUNCATED AT 250 WORDS)
Lee
P D
PD
Children's Hospital, Denver, Colorado 80218.
Wilson
D M
DM
Rountree
L
L
Hintz
R L
RL
Rosenfeld
R G
RG
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005069:Evaluation Studies as Topic; D005260:Female; D006130:Growth Disorders / Q000097:blood / Q000175:diagnosis*; D013006:Growth Hormone / Q000172:deficiency*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008297:Male; D013002:Somatomedins / Q000032:analysis*
D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone